Objectives to be achieved by this invention are the provision of a method for determining the ultimate fuselage shape of supersonic aircraft by integral modification of the upper and lower surface shapes of the fuselage, to reduce sonic boom without increasing wave drag, as well as the provision of such a fuselage front section shape. A method for determining the fuselage shape of an aircraft for supersonic flight of this invention employs different methods of determining the fuselage lower-surface shape and the fuselage upper-surface shape, whose upper and lower boundary is defined for each fuselage cross-section by the horizontal line including two points at which the fuselage width from the bilateral symmetry plane is maximum. The above fuselage lower-surface shape is determined by optimization of an objective function to minimize the pressure increase amount of the sonic boom pressure waveform on the ground, estimated using a panel method and waveform parameter method; the fuselage upper-surface shape is determined by optimization of an objective function so as to minimize drag, estimated using a panel method.